This invention relates to a color picture-in-picture television receiver in which a reduced picture of one (called "B" hereinafter) station channel broadcast is formed in a picture of another (called "A" hereinafter) station channel broadcast on a single screen, and more particularly to a color picture-in-picture television receiver in which the reduced picture is improved in horizontal resolution.
In a conventional picture-in-picture television receiver, video signals of the B channel broadcast (designated by "S.sub.B " hereinafter) are alternately written into two field memories every field. While the video signals are written into the one field memory, the video signals are read out from the other field memory. The read out video signals are inserted into a blanking interval formed at a predetermined portion of the video signals of the A channel broadcast station (designated by "S.sub.A " hereinafter). A charge-coupled Device (CCD) or a Bucket-Brigade Device (BBD) consisting of charge transferring elements is used for the field memory. The signals S.sub.B are sampled by writing pulses of a predetermined frequency. The sampled signals S.sub.B are written into the field memory. The signals S.sub.B are not sampled at the times between the successive writing pulses. Accordingly, the reduced picture is deteriorated in horizontal resolution. In a method to remove such deterioration, one train of writing pulses to be applied to the one field memory is made to be opposite in phase to another train of writing pulses to be applied to the other field memory. Thus, the video signals S.sub.B are sampled by the one train of writing pulses at times corresponding to the times when the video signals S.sub.B are not sampled by the other train of writing pulses to be written into the one field memory. This method is useful for video signals S.sub.B which are black-and-white television signals. However, when R(Red)-, G(Green)- and B(Blue)-components of color television video signals S.sub.B are sampled at the same time by any one of the writing pulses, the picture flickers and a vertical line in the picture becomes a notched line.